The higher the number the longer the delay, the lower the number the quicker the memory controller/CPU can have access the data.
The higher the frequency the higher the timings will generally be.
e.g. (Generalisation of timings that can be found vs frequency)
1600MHz -- 8,8,8,24
1866MHz -- 9,9,9,24
2000MHZ -- 10,10,10,28
2133MHz -- 10,11,11,28